The goal of the proposed program is to discover small molecules as potent and specific binders of HIV-1 RNA sequences. In particular, inhibitors of key regulatory protein-RNA interactions (i.e., Rev-RRE and Tat-TAR) will be synthesized and studied. The specific aims of this proposal are: (a) To develop a screening assay for identifying high-affinity and selective HIV-1 Rev-RRE inhibitors, (b) To develop a screening assay for identifying potent and selective Tat-Tar binders, (d) To develop novel RRE binders based on octahedral Ru/II complexes, (e) To develop specific RRE binders based on backbone- cyclized peptides, (f) To identify potent viral RNA binders and to determine their binding characteristics, (g) To test the most promising binders for their ability to inhibit Rev and Tat function in vivo, and (h) To test the most promising binders for their ability to inhibit HIV-1 replication. Novel assays for rapid screening of potential viral RNA binders are proposed. The assays rely on the release of a fluorescently-tagged peptide from a immobilized peptide-RNA complex. The modular and sensitive assays can be executed in the presence of competitors and at different stringency levels. Modular synthetic approaches for new RRE and TAR binders, via the generation of molecular diversity, are proposed. Rapid construction of biased libraries will be achieved using multiple component condensation (MCC) reactions. In addition, novel Ru/II coordination compounds and novel backbone-cyclized peptides will be synthesized as specific RRE binders. The compounds prepared will be screened for their ability to inhibit Rev-RRE and Tat-TAR binding using the proposed novel assays. The most promising inhibitors will be tested for their inhibitory capability in vivo and ultimately for their ability to inhibit HIV replication. The emergence of resistant viral strains necessitates the development of new directions and novel strategies for anti-HIV drug design. Small molecules that target pivotal viral RNA sites, and can specifically prevent the formation of key regulatory RNA-protein complexes, are proposed as promising candidates for anti-retroviral drug discovery. The proposed integrated approach will yield new families of effective and specific inhibitors of Rev-RRE and Tat-TAR binding. Potent and specific inhibitors of these essential regulatory events will significantly advance the development of highly active anti-retroviral agents.